<!DOCTYPE html>
<title>CSS Test (Display): <slot> elements should be focusable</title>
<link rel="author" title="L. David Baron" href="https://dbaron.org/">
<link rel="author" title="Google" href="http://www.google.com/">
<link rel="help" href="https://html.spec.whatwg.org/multipage/rendering.html#flow-content-3">
<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/2632">
<link rel="help" href="https://github.com/whatwg/html/issues/1837">
<link rel="help" href="https://github.com/whatwg/html/pull/9425">
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1366037">
<!--

  This requirement is not particularly clear from current specs,
  so this test is tentative.  See issues above.

-->
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<body>

<script>

  function do_test(slot_style, description) {
    test(
      function() {
        let host = document.createElement("div");
        document.body.appendChild(host);
        var root = host.attachShadow({mode:"open"});
        root.innerHTML = `
          <style>
            slot       { --test-value: slot-not-focused; }
            slot:focus { --test-value: slot-is-focused; }
          </style>
          <slot tabindex="1" style="${slot_style}"></slot>
        `;
        let slot = root.querySelector("slot");
        let cs = getComputedStyle(slot);
        assert_not_equals(root.activeElement, slot, "precondition");
        assert_equals(cs.getPropertyValue("--test-value"), "slot-not-focused", "precondition (style)");
        slot.focus();
        assert_equals(root.activeElement, slot, "slot is now focused");
        assert_equals(cs.getPropertyValue("--test-value"), "slot-is-focused", "slot is now focused (style)");
        document.body.removeChild(host);
      }, `slot element with ${description} should be focusable`);
  }

  do_test("display: block", "display: block");
  do_test("", "default style");

</script>

